Forage Sampling Procedures
By: Warren Rusche, SDSU Extension Beef Feedlot Management Associate
Proper sampling of forage is essential if we want to obtain an accurate indication of the nutrient composition, dry matter content, or value of any feedstuff. Correct sampling and analysis is even more important under conditions that might increase feedstuff variability, such as challenging growing conditions. Sampling procedures vary depending upon the type of forage and whether or not sampling occurs pre-harvest or after the forage has been stored.
Forage in a Windrow Prior to Baling
With a sharp shears, cut 6-inch sections from several locations in the windrow. If the forage is dry, take extreme care to avoid losing leaves. Cut the sections into pieces about 1 inch long and mix samples in a clean container.
Forage Prior to Silage Harvest
If forage in the windrow or standing corn or sorghum is to be harvested with a forage chopper, several rounds can be chopped from a representative part of the field. Collect small samples from various locations in the forage wagon, and mix thoroughly in a clean container. As an alternative method, a representative sample of standing forage can also be cut off, run through a chipper, and then a sub-sample of the chopped material used for moisture testing.
Use a hay probe to collect samples. For large round bales the probe should be inserted from the rounded side into the center of the bale. Square bales should be probed from the middle of the butt end. More detailed instructions on sampling baled hay can be found on a video “Forage Hay Sampling Method” produced by SDSU Extension.
For bagged silage, collect about 2 gallons of silage by taking handfuls at random from about 10 locations and mix them in a clean container. With bunkers or piles, the best method is to remove silage from multiple locations in the face using a loader or silage facing tool, and then subsampling from the removed material. Grabbing samples by hand from the exposed face greatly increases the risk of being trapped in an avalanche, particularly as the sizes of bunkers or piles increase.
When Should Forage Be Sampled?
Forage samples should be collected as closely as possible to when the samples will be analyzed and when management decisions will be made. Sampling pre-harvest allows producers to pin-point moisture content and harvest timing. The microwave method is a low-cost way to test for dry matter content on the farm with minimal turn-around time. A detailed explanation of that procedure can be found in this article.
Sampling immediately after harvest provides valuable information for marketing feedstuffs or for making longer-term feeding plans. Collecting a sample close to when the feed will be fed will provide the most accurate estimate of actual feed value and account for any storage or weathering losses that may occur post-harvest.
Regardless of when the sample is taken, it should be analyzed as quickly as possible. You can freeze samples to be shipped later, but minimizing the delay reduces the risk that the sample composition will significantly change. Mail or deliver samples early in the week for best results.
Make sure that the sample collected is representative of the lot of forage. Changes in fields, maturity, hybrids, or other factors mean that a different sample should be taken. Within each lot, taking more small samples from a variety of bales or locations within a silage pile is preferable to fewer, larger quantities. Finally, make sure to label the containers well so as not to rely on memory.